U.S. patent application number 11/077896 was filed with the patent office on 2005-09-22 for process for the synthesis of cxcr4 antagonist.
Invention is credited to Baird, Ian R., Chen, Gang, Crawford, Jason B., Gauthier, David, Skerlj, Renato, Wilson, Trevor R..
Application Number | 20050209277 11/077896 |
Document ID | / |
Family ID | 34993619 |
Filed Date | 2005-09-22 |
United States Patent
Application |
20050209277 |
Kind Code |
A1 |
Crawford, Jason B. ; et
al. |
September 22, 2005 |
Process for the synthesis of CXCR4 antagonist
Abstract
This invention relates to a process for synthesizing
heterocyclic pharmaceutical compound which binds to the CXCR4
chemokine receptor. In one embodiment, the process comprises: a)
reacting a 5,6,7,8-tetrahydroquinolinylamine and an alkyl aldehyde
bearing a phthalimide or a di-tertiary-butoxycarbonyl (di-BOC)
protecting group to form an imine; b) reducing the imine to form a
secondary amine; c) reacting the secondary amine with a haloalkyl
substituted heterocyclic compound, to form a phthalimido-protected
or di-tert-butoxycarbonyl protected tertiary amine; and d)
hydrolyzing the protected amine to obtain a compound having Formula
I' 1
Inventors: |
Crawford, Jason B.; (British
Columbia, CA) ; Chen, Gang; (British Columbia,
CA) ; Gauthier, David; (British Columbia, CA)
; Skerlj, Renato; (Vancouver, CA) ; Baird, Ian
R.; (Abbotsford, CA) ; Wilson, Trevor R.;
(Langley, CA) |
Correspondence
Address: |
MORRISON & FOERSTER LLP
3811 VALLEY CENTRE DRIVE
SUITE 500
SAN DIEGO
CA
92130-2332
US
|
Family ID: |
34993619 |
Appl. No.: |
11/077896 |
Filed: |
March 11, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60553589 |
Mar 15, 2004 |
|
|
|
Current U.S.
Class: |
514/314 ;
546/176 |
Current CPC
Class: |
C07D 401/14 20130101;
A61P 31/18 20180101; C07D 215/40 20130101; C07D 401/12 20130101;
Y02P 20/55 20151101; A61P 43/00 20180101 |
Class at
Publication: |
514/314 ;
546/176 |
International
Class: |
A61K 031/4709; C07D
043/02 |
Claims
We claim:
1. A process for synthesizing a compound having Formula I',
24wherein R, R.sup.1, R.sup.2 and R.sup.3 are non-interfering
substituents; k is 0-3; m is 0-4 and n is 1-6, comprising: (a)
reacting a 5,6,7,8-tetrahydroquino- linylamine optionally
substituted with R.sup.1 with an alkyl aldehyde bearing a
phthalimide protecting group or a di-tert-butoxycarbonyl protecting
group to produce an imine; (b) reducing the imine in an organic
solvent with a metal hydride reducing reagent and either an organic
acid or a metal salt to form a secondary amine; (c) reacting the
secondary amine with a 2-halomethylbenzimidazole optionally
substituted with R.sup.3 and optionally bearing a benzimidazole
amine protecting group or other amine substitution (R.sup.2) to
form a phthalimido-protected or a di-tert-butoxycarbonyl-protected
tertiary amine; and (d) hydrolyzing the protected tertiary amine to
obtain the Formula I' compound.
2. The process of claim 1, further comprising treating the Formula
I compound with decolorizing carbon or silica gel to remove
impurities.
3. The process of claim 1, wherein said
5,6,7,8-tertrahydroquinolinylamine is a racemic mixture.
4. The process according to claim 3, wherein the Formula I'
compound is a racemic mixture.
5. The process of claim 4, further comprising isolating an (R) or
(S) enantiomer via selective crystallization in a crystallization
solvent.
6. The process of claim 1, wherein said
5,6,7,8-tetrahydroquinolinylamine is an optically active (S)
enantiomer.
7. The process of claim 6, wherein the Formula I' compound is an
optically active (S) enantiomer.
8. The process of claim 1, wherein said
5,6,7,8-tetrahydroquinolinylamine is an optically active (R)
enantiomer.
9. The process of claim 8, wherein the Formula I' is an optically
active (R) enantiomer.
10. The process of claim 1, wherein R, R.sup.1, R.sup.2 and R.sup.3
are each absent or are independently selected from the group
consisting of hydrogen, halo, nitro, cyano, carboxylic acid, alkyl,
alkenyl, cycloalkyl, hydroxyl, thiol, amino, acyl, carboxylate,
carboxamide, sulfonamide, an aromatic group and a heterocyclic
group.
11. The process of claim 10, wherein R, R.sup.1, R.sup.2 and
R.sup.3 are each absent or are independently selected from the
group consisting of alkyl(C.sub.1-10), alkenyl(C.sub.2-10),
alkynyl(C.sub.2-10), aryl(C.sub.5-12), arylalkyl, arylalkenyl, and
arylalkynyl.
12. The process of claim 11, wherein at least one of R, R.sup.1,
R.sup.2 and R.sup.3 contain one or more heteroatoms selected from
the group consisting of O, S, and N.
13. The process of claim 1, wherein the alkyl aldehyde is an ethyl
aldehyde, a propyl aldehyde, a butyl aldehyde or a pentyl
aldehyde.
14. The process of claim 1, wherein the dehydrating agent in step
(a) is potassium carbonate, sodium carbonate, sodium bicarbonate or
magnesium sulfate.
15. The process of claim 1 wherein the reducing agent in step (b)
is sodium borohydride, and the organic acid is selected from the
group consisting of acetic acid, propionic acid and zinc
chloride.
16. The process of claim 1, wherein step (b) is performed at a
reduced temperature of -25 to -5.degree. C.
17. The process of claim 1, wherein the organic solvent in step (c)
further comprises an amine base and a catalytic amount of
iodide.
18. The process of claim 17, wherein the amine base is
diisopropylethylamine.
19. The process of claim 1, wherein the elevated temperature in
step (c) is 40-60.degree. C.
20. The process of claim 1, wherein R.sup.2 is a t-butoxycarbonyl
amine protecting group.
21. The process of claim 20, wherein removal of the amine
protecting group in step (d) is performed at a pH 3 under aqueous
conditions.
22. The process of claim 1, wherein removal of the phthalimide
protecting group in step (d) is performed with hydrazine, ethylene
diamine, n-butylamine or methylamine.
23. The process of claim 1, further comprising a purification step
for purifying the Formula I' compound.
24. The process of claim 23, wherein the Formula I' compound is
extracted into a mildly acidic aqueous solution followed by
treatment with an activated carbon.
25. The process of claim 23, wherein an organic solution of the
Formula I' compound is treated with activated carbon followed by
filtration and extraction into a mildly acidic aqueous
solution.
26. The process of claim 23, wherein the purification step includes
extraction of a basic aqueous solution of the Formula I' compound
with dichloromethane, followed by silica gel flash
chromatography.
27. The process of claim 23, wherein the purification step includes
reducing hydrazine levels to pharmaceutically acceptable levels
through extraction of a dichloromethane solution of the Formula I'
compound with aqueous sodium hydroxide.
28. The process of claim 5, wherein the crystallization solvent is
isopropyl acetate.
29. The process of claim 5, wherein the crystallization solvent is
ethyl acetate, tetrahydrofuran or dichloromethane.
30. The process of claim 23, further comprising a co-distillation
procedure to control residual dichloromethane levels.
31. The process of claim 5 further comprising the step of
concentrating the Formula I' compound to dryness prior to the
crystallization step.
32. The process of claim 5, wherein the crystallization solvent is
isopropyl acetate or ethyl acetate, and the crystallization step is
performed at a temperature of 50-65.degree. C. to achieve solvation
with the crystallization solvent.
33. The process of claim 5, wherein the crystallization step
further comprises seeding a solution of the Formula I' compound
with crystalline Formula I' compound to initiate
crystallization.
34. The process of claim 5, wherein the crystallization step is
performed while agitating a solution of the Formula I' compound to
control particle size of the Formula I' compound crystals.
35. The process of claim 5, wherein the Formula I' compound
crystals are dried in a vacuum oven to lower residual solvent
levels.
36. The process of claim 1, wherein the Formula I' compound is
selected from the group consisting of
(S)--N'-(1H-benzimidazol-2-ylmethyl)-N'-5,6,-
7,8-tetrahydroquinolin-8-yl-1,4-butanediamine;
(R)--N'-(1H-benzimidazol-2--
ylmethyl)-N'-5,6,7,8-tetrahydroquinolin-8-yl-1,4-butanediamine; and
(R,S)--N'-(1H-benzimidazol-2-ylmethyl)-N'-5,6,7,8-tetrahydroquinolin-8-yl-
-1,4-butanediamine.
37. The process of claim 1, wherein said secondary imine is
N-[(1,3-dioxo-1,3-dihydroisoindol-2-yl)-alkyl)]-tetrahydroquinolinylamine-
,
(S)-2-[4-(5,6,7,8-tetrahydroquinolin-8-ylamino)-butyl]-isoindole-1,3-dio-
ne;
(R)-2-[4-(5,6,7,8-tetrahydroquinolin-8-ylamino)-butyl]-isoindole-1,3-d-
ione;
(R,S)-2-[4-(5,6,7,8-tetrahydroquinolin-8-ylamino)-butyl]-isoindole-1-
,3-dione; or an imine having the formula 25
38. The process of claim 1, wherein the phthlamido-protected
tertiary amine compound is
N-{[(benzimidazol-2-yl)methyl-(1,3-dioxo-1,3-dihydroiso-
indol-2-61)-alkyl]-tetrahydroquinolinyl}amine;
(S)-2-{4-[(1H-benzimidazol--
2-ylmethyl)-(5,6,7,8-tetrahydroquinolin-8-yl)-amino]-butyl}-isoindole-1,3--
dione;
(R)-2-{4-[(1H-benzimidazol-2-ylmethyl)-(5,6,7,8-tetrahydroquinolin--
8-yl)-amino]-butyl}-isoindole-1,3-dione; or
(R,S)-2-{4-[(1H-benzimidazol-2-
-ylmethyl)-(5,6,7,8-tetrahydroquinolin-8-yl)-amino]-butyl}-isoindole-1,3-d-
ione.
39. The process of claim 1, wherein the
di-tert-butoxycarbonyl-protected tertiary amine has the formula 26
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. provisional patent
application Ser. No. 60/553,589, filed Mar. 15, 2004, which is
incorporated by reference in this application.
TECHNICAL FIELD
[0002] This invention relates to a process for synthesizing
heterocyclic pharmaceutical compounds which bind to the CXCR4
chemokine receptor.
BACKGROUND OF THE INVENTION
[0003] It is desired by those with skill in the art to develop
efficient and reliable synthetic routes to pure and stable forms of
pharmaceutical compounds. As examples, the novel heterocyclic
compounds disclosed in WO 0056729 demonstrate protective effects
against infection of target cells by human immunodeficiency virus
(HIV).
[0004] The chemotactic cytokines, or chemokines, are a family of
proteins, approximately 8-10 kDa in size that function, at least in
part by modulating a complex and overlapping set of biological
activities important for the movement of lymphoid cells and
extravasation and tissue infiltration of leukocytes in response to
inciting agents (see, for example: P. Ponath, Exp. Opin. Invest.
Drugs, 7:1-18, 1998). The cellular receptors for these proteins are
classified based on the chemokine natural ligand. Receptors of the
.beta.-chemokines are designated with the prefix "CCR," whereas the
receptors of the .alpha.-chemokine are designated with the prefix
"CXCR".
[0005] The natural chemokine ligand for the CXCR4 receptor is
stromal cell-derived factor-1 (SDF-1). The inhibition of the
binding of SDF-1 to CXCR4 by specific small-molecule inhibitors has
been shown in a model, to reduce the severity of the pathogenesis
of collagen II-induced arthritis (Matthys et al., J. Immunol. 107:
4686-4692, 2001). This model, which is used as a study model for
the pathogenesis of rheumatoid arthritis in humans, shows that
SDF-1 plays a central role in the pathogenesis of murine collagen
induced arthritis. Similarly, the use of small-molecule CXCR4
inhibitors has been shown in a murine model, to reduce a number of
pathological parameters related to asthmatic-type inflammation in
an allergin-induced inflammation (Lukacs et al., Am. J. Pathology,
160 (4): 1353-1360, 2002).
[0006] Two specific chemokine receptors, CXCR4 and CCR5, have been
implicated in the etiology of infection by human immunodeficiency
virus (HIV). The T cell-line tropic (T-tropic) viral phenotype of
HIV requires, for infection, an association with the CXCR4
receptor, which is expressed in the surface of certain cells of the
immune system (Carroll et al., Science, 276: 274-276, 1997).
Specifically, an interaction between HIV and the CXCR-4 receptor is
required for membrane fusion, a necessary step in the infection of
the host immune cell.
[0007] The novel heterocyclic compounds disclosed in U.S. Pat.
No.5,583,131, U.S. Pat. No. 5,698,546 and U.S. Pat No. 5,817,807
selectively bind to the CXCR4 receptor, inhibiting the binding of
the natural SDF-1 ligand. Such binding may show anti-inflammatory
effects. The binding also competitively prevents the binding of the
T-tropic HIV with the receptor, and thus imparts a preventative
effect against HIV infection.
[0008] The compound AMD3100, which is a specific CXCR4 antagonist,
has been shown to reduce HIV viral load and X4 (T-tropic) virus
levels in humans (D. Schols et al. Presented at: 9.sup.th
Conference on Retroviruses and Opportunistic Infections, Feb.
24-28, 2002, Washington State Convention and Trade Center, Seattle,
Wash.).
[0009] This invention describes the processes for the efficient
synthesis and isolation of pure forms of these compounds.
SUMMARY OF THE INVENTION
[0010] The invention provides a process for synthesizing
heterocyclic pharmaceutical compounds which bind to the CXCR4
chemokine receptor. In a particular embodiment, the invention
provides a process for synthesizing an optionally substituted (R),
(S) or (RS) (N'-(1H-benzimidazol-2-ylmethy-
l)-N'-5,6,7,8-tetrahydroquinolin-8-yl-1,4-alkylamine) having
formula I' 2
[0011] Generally, the process comprises: a) reacting a
5,6,7,8-tetrahydroquinolinylamine with an alkyl aldehyde bearing a
phthalimido or a di-tertiary-butoxycarbonyl (di-BOC) protecting
group to form an imine; b) reducing the imine to form a secondary
amine; c) reacting the secondary amine with a haloalkyl substituted
heterocyclic compound; and d) removing the amino-protecting groups.
Optional steps include a decolorizing and/or purifying treatment,
and a process for the crystallization of the compound.
[0012] In Formula I', R, R.sup.1, R.sup.2 and R.sup.3 are
non-interfering substituents; k is 0-3; m is 0-4 and n is 1-6. In
one embodiment, R, R.sup.1, R.sup.2 and R.sup.3 are each
independently selected from the group consisting of hydrogen, halo,
nitro, cyano, a protected carboxylic acid, alkyl, alkenyl,
cycloalkyl, a protected hydroxyl, a protected thiol, a protected
amino, acyl, carboxylate, carboxamide, sulfonamide, an aromatic
group and a heterocyclic group. In addition, R, R.sup.1, R.sup.2
and R.sup.3 may be absent. By "protected," it is meant that the
group is rendered unreactive by protecting it with an additional
nonreactive chemical moiety which may later be selectively
removed.
[0013] More particularly, when the non-interfering substituent is
alkyl, alkenyl or cycloalkyl, it may be alkyl(C.sub.1-10),
alkenyl(C.sub.2-10), alkynyl(C.sub.2-10), aryl(C.sub.5-12),
arylalkyl, arylalkenyl, or arylalkynyl, each of which may
optionally contain one or more heteroatoms selected from O, S, and
N and each of which may further be substituted; or optionally
substituted forms of acyl, arylacyl, alkyl- alkenyl-, alkynyl- or
arylsulfonyl and forms thereof which contain heteroatoms in the
alkyl, alkenyl, alkynyl or aryl moieties. Other noninterfering
substituents include OR, SR, NR.sub.2, COOR, CONR.sub.2, where R is
H or alkyl, alkenyl, alkynyl or aryl as defined above. Where the
substituted atom is C, the substituents may include, in addition to
the substituents listed above, halo, OOCR, NROCR, where an R is H
or a substituent set forth above, or may be .dbd.O.
[0014] In general, a "noninterfering substituent" is a substituent
whose presence does not destroy the ability of the compound of
Formula I' to behave as a chemokine antagonist. Specifically, the
presence of the substituent does not destroy the effectiveness of
the compound. Because the compounds of the present invention have
been shown to inhibit HIV replication, and have been shown to have
anti-inflammatory effects by specifically interacting with the
CXCR4 receptor, the compounds of the invention are effective in
treating conditions which require modulation of CXCR4 mediated
activity.
[0015] In one aspect, the invention provides a method for
synthesizing a compound having Formula I', comprising:
[0016] a) reacting an optionally substituted (R.sup.1)
5,6,7,8-tetrahydroquinolinylamine ((R), (S) or (R,S)) with an alkyl
aldehyde bearing a phthalimide protecting group or a
di-tert-butoxycarbonyl (di-BOC) protecting group in an organic
solvent with or without a dehydrating agent to produce an
imine;
[0017] b) reducing the imine in an organic solvent with a metal
hydride reducing reagent in the presence of an organic acid or a
metal salt to form a secondary amine;
[0018] c) reacting the secondary amine with an optionally
substituted 2-halomethylbenzimidazole optionally bearing a
benzimidazole amine protecting group or other amine substituent in
an organic solvent to form a phthalimido-protected or
di-tert-butoxycarbonyl-protected tertiary amine; and
[0019] d) hydrolyzing the protected tertiary amine to obtain a
compound having Formula IA'.
[0020] In one example as shown in Scheme 1, step a) comprises
reacting an optionally substituted (R.sup.1)
5,6,7,8-tetrahydroquinolinylamine ((R), (S) or (RS)) with an alkyl
aldehyde bearing a phthalimide protecting group having Formula III'
(or a 1,3-dioxo-1,3-dihydroisoindol-2-yl)-alkyl aldehyde) to form
an imine having Formula IV' via condensation (Scheme 1a).
Alternatively, the alkyl aldehyde may bear a di-BOC protecting
group having Formula IIa' to form an imine having Formula IVa' via
condensation (Scheme 1b). The alkyl aldehyde is preferably an ethyl
aldehyde, a propyl aldehyde, a butyl aldehyde or a pentyl aldehyde.
3
[0021] In another example as shown in Scheme 2, step b) comprises
reducing an imine having Formula IV' in an organic solvent with a
metal hydride reducing reagent and either an organic acid or a
metal salt to form an
N-[(1,3-dioxo-1,3-dihydroisoindol-2-yl)-alkyl]-tetrahydroquinolinylamine
having Formula V' (Scheme 2a). Alternatively, an imine having
Formula IVa' may be reduced to form a secondary amine hydrochloride
salt having Formula Va' (Scheme 2b). 4
[0022] In yet another example as shown in Scheme 3, step c)
comprises reacting a secondary amine having formula V'
(N-[(1,3-dioxo-1,3-dihydrois-
oindol-2-yl)-alkyl]-tetrahydroquinolinylamine) with an optionally
substituted (R.sup.3) 2-halomethylbenzimidazole (Formula VI'). In
one example, step c) comprises reacting the secondary amine with
2-halomethylbenzimidazole in an organic solvent at elevated
temperature under basic conditions to form a
N-{[(benzimidazol-2-yl)methyl-(1,3-dioxo-
-1,3-dihydroisoindol-2-yl)-alkyl]-tetrahydroquinolinyl}amine having
Formula VII' (Scheme 3a). Alternatively, alkylation of a secondary
amine HCl salt having Formula Va' with a 2-halomethylbenzimidazole
as previously described results in a protected tertiary amine
having Formula VIIa' (Scheme 3b).
[0023] In Formula VI' in Scheme 3, X may be any halo leaving group,
such as chlorine, bromine and iodine. The (R.sup.3)
2-halomethylbenzimidazole (Formula VI') may further be substituted
with a benzimidazole amine protecting group or other amine
substituent (R.sup.2). 5
[0024] In another example as shown in Scheme 4, step d) comprises
sequentially or simultaneously hydrolyzing the benzimidazole
amine-protecting group (formula VII' or formula VIIa'), if present,
and the phthalimide or di-BOC protecting group to obtain the
compound according to Formula I' (Scheme 4). 6
[0025] The process of the present invention may further comprise
the steps of:
[0026] (a) treating the Formula I' compound with decolorizing
carbon and silica gel to remove impurities; and
[0027] (b) in the case of an optically active Formula I' compound,
isolating the
N'-(1H-benzimidazol-2-ylmethyl)-N'-5,6,7,8-tetrahydroquinol-
in-8-yl-alkyldiamine (I') as a crystalline material (as the (R) or
(S) enantiomer) via a selective crystallization process.
[0028] In an exemplary embodiment, the process is used to
synthesize an unsubstituted (S)
(N'-(1H-benzimidazol-2-ylmethyl)-N'-5,6,7,8-tetrahydroq-
uinolin-8-yl-1,4-butanediamine) (Formula I). It should be readily
apparent to those of ordinary skill in the art that the process
remains essentially the same whether the ultimate compound is
substituted or not, and/or whether the process results in a product
that consists of a single enantiomer or a mixture of
enantiomers.
[0029] In one aspect as shown in Schemes 5-8, the process for
synthesizing a compound having Formula I, comprises:
[0030] (a) reacting an unsubstituted
(5,6,7,8-tetrahydroquinolin-8-yl)-ami- ne (S) with a
1-(1,3-dioxo-1,3-dihydroisoindol-2-yl)-butan-4-al in an organic
solvent in the presence of a metal carbonate salt to produce an
imine via a condensation;
[0031] (b) reducing the imine in an organic solvent with a metal
hydride reducing reagent and either an organic acid or a metal salt
to form an a
N-{[1-(1,3-dioxo-1,3-dihydroisoindol-2-yl)-butan-4-yl]-(5,6,7,8-tetrahydr-
oquinolin-8-yl)}-amine;
[0032] (c) reacting the
N-{[1-(1,3-dioxo-1,3-dihydroisoindol-2-yl)-butan-4-
-yl]-(5,6,7,8-tetrahydroquinolin-8-yl)}-amine with
2-chloromethylbenzimida- zole bearing a butoxycarbonyl moiety as
the benzimidazole amine protecting group in an organic solvent at
elevated temperature under basic conditions to form an
N-{[1-(1,3-dioxo-1,3-dihydroisoindol-2-yl)-butan-4--
yl]-[(benzimidazol-2-yl)-methyl]-(5,6,7,8-tetrahydroquinolin-8-yl)}-amine;
and
[0033] (d) sequentially or simultaneously hydrolyzing the
benzimidazole amine-protecting group and the phthalimide protecting
group to obtain the compound according to Formula I.
DETAILED DESCRIPTION OF THE INVENTION
[0034] Many pharmaceutical compounds are produced through
multi-step chemical syntheses. Each chemical step in the process
should efficiently deliver a pure compound. To achieve this goal,
each step must be experimentally optimized to enhance both yields
and product purities. There is often a requirement, at the end of
the synthesis, for a final purification of the biologically active
pharmaceutical compound to ensure that it is free of potentially
toxic side products or other impurities.
[0035] One of the synthetic components of the novel heterocyclic
compounds described in this invention, the optionally substituted
5,6,7,8-tetrahydroquinoline (Skupinska et al., J. Org. Chem.
67(22): 7890-7893, 2002), is an optically active compound. The
description of the synthesis and isolation of the unsubstituted
compound (Formula II) is described in WO 2003022785. "Optically
active" denotes the ability of a compound to rotate the plane of
plane-polarized light. In each case of optical activity of a pure
compound, there are two and only two isomers, called "enantiomers",
which have identical physical properties except that they rotate
the plane of polarized light in opposite directions in equal
amounts. The rotation of one enantiomer will be clockwise, called
dextrotatory, abbreviated "D" or (+), and the rotation of the other
enantiomer will be counterclockwise, called levorotatory,
abbreviated "L" or (-). Additionally, the prefixes R and S, based
on the spatial arrangement of substituents about a chiral center,
are used to denote absolute stereochemistry. There is no
correlation between the nomenclature for absolute stereochemistry
and the direction of rotation of plane polarized light. (See, for
example, March, J. Advanced Organic Chemistry: Reactions,
Mechanisms and Structures, 4.sup.th Edition, Chapter 4, John Wiley
& Sons, USA, 1992).
[0036] The term "enantiomeric excess" or "ee" is related to the
term "optical purity" in that both are measurements of the same
phenomenon. The value of ee is a percentage measurement of the
optical purity, with 100 being a pure single, enantiomer. Hence, a
compound that is 95% optically pure is 95% ee. The percent optical
purity for a given sample is defined as: 1 Percent optical purity =
[ ] observed [ ] maximum .times. 100
[0037] As shown, [.alpha.] observed is the observed angle of
rotation of plane polarized light and [.alpha.] max is the maximum
rotation possible (the rotation that would be observed for a single
enantiomer). The enantiomeric excess is also related to absolute
configuration, and is measured as the percentage excess of one
enantiomer over the other as follows: 2 ee = [ R ] - [ S ] [ R ] +
[ S ] .times. 100 = % R - % S
[0038] Enantiomers of chiral drugs may differ considerably in their
pharmacological and toxicological effects because they interact
with biological macromolecules, the majority of which are
stereoselective (Drayer, Clin. Pharmacol Ther. 40:125 (1986)).
Hence, it is often desired by those with skill in the art to
isolate the drug as a single enantiomer in a pure form. In the case
of the 8-amino-5,6,7,8-tetrahydroquinoline, an enzymatic kinetic
resolution provides the (S)-enantiomer in high enantiopurity (97%
ee). The (R)-enantiomer can also be isolated in high enantiopurity.
(See, WO 2003022785).
[0039] The optical activity of a compound can potentially be
further enhanced through a direct crystallization (Li et al., J.
Pharm. Sci. 86(10):1073 (1997)). The molecular chirality of a given
compound is expressed in its overall crystallography, so it is
sometimes possible to achieve an enantiomeric resolution
spontaneously through the course of the crystallization. A
crystalline solid is characterized by a high degree of internal
order, consisting of a three-dimensional translational repetition
of a basic structural pattern (Brittain, H. G. Pharmaceutical
Research, 7(7), 683-690, 1990). Hence, it is also possible to
reject other side-product impurities during the crystallization
process. Disclosed in this invention is a detailed description of a
crystallization process which serves to increase both the
enantiopurity as well as the overall purity of the Formula I'
compound.
[0040] The present invention is directed to the compounds according
to Formula I' which demonstrate a protective effect against HIV
infection by inhibiting the binding of HIV to the chemokine
receptor CXCR4. The Formula I' compounds also display an
anti-inflammatory effect, as shown in murine models, by inhibiting
the binding of the natural chemokine SDF-1 to the chemokine
receptor CXCR4. This invention, in particular, describes various
methods for the synthesis and isolation of pure forms of the
compounds as described below. The experimental procedures use the
(S) enantiomer as an example, but the procedures are also valid for
the (R) enantiomer or the (RS) racemate.
[0041] Schemes 5-8 illustrate the synthesis of a compound having
Formula I. The same procedure may be utilized when making
substituted derivatives of Formula I compounds (i.e., compounds
having Formula I'). Accordingly, when a compound according to
Formula "X" is exemplified below, the description also applies to
the use of Formula "X'" compounds as well. Furthermore, it should
be understood that the reaction conditions shown in Schemes 5-8
below are only exemplary, and can be further optimized by using
alternative reagents and/or conditions based on well-known chemical
principles and protocols, as well as the teachings herein.
[0042] Imine Formation
[0043] This invention provides a process for the efficient
formation of an amino-substituted 5,6,7,8-tetrahydroquinoline of
Formula II with an alkyl aldehyde of Formula III, as illustrated in
Scheme 5. 7
[0044] As a preliminary step, the amino-substituted
5,6,7,8-tetrahydroquinoline hydrochloride salt is treated with an
aqueous base such as 10% sodium hydroxide and extracted with an
organic solvent such as dichloromethane to isolate the amine
freebase. In the preferred process, an optically active amine is
used as a reagent (as depicted in Formula II), with the preferred
isomer being the (S)-isomer.
[0045] Then, a stoichiometrically equal mixture of the
8-amino-5,6,7,8-tetrahydroquinoline amine freebase (Formula II) and
the aldehyde (Formula III) are reacted in an organic solvent in the
presence of an anhydrous inorganic salt. See, for example: Hamilton
et al., Tetrahedron Lett., 34:2847-2850 (1993) and Balenovi et al.,
J. Org. Chem. 17:1459-1560 (1952). Exemplary organic solvents
include, without limitation, diethyl ether, dimethylformamide,
ethyl acetate, dichloromethane, chloroform, tetrahydrofuran,
acetonitrile, ethylene glycol dimethyl ether, toluene and benzene
with a preferred solvent being tetrahydrofuran.
[0046] Examples of inorganic salts include, but are not limited to,
anhydrous magnesium sulfate, potassium carbonate, magnesium
carbonate, sodium sulfate and sodium bicarbonate with a preferred
inorganic salt being anhydrous potassium carbonate as shown in
Scheme 5. Salt loading ranges from 0.5 to 2.0 stoichiometric
equivalents, with 1.0 stoichiometric equivalent being preferred.
Other dehydrating agents, such as molecular sieves, can also be
used. In the case of toluene or benzene solvents, a Dean-Stark trap
(filled with molecular sieves) can be employed in the reaction to
remove water.
[0047] Reaction concentrations typically range from 0.05 M to 2.0 M
with a preferred concentration of reagent II and III being in the
0.5 M range. The course of the reaction can be readily followed by
.sup.1H nuclear magnetic resonance (NMR) spectroscopy. Temperatures
for the reaction are from -20.degree. C. to reflux, with a
preferred temperature being near ambient temperature, or 23.degree.
C.
[0048] The imine is typically isolated via filtration of the
reaction mixture (to remove the inorganic salt) through a glass
frit, filter paper or other form of filter. Generally, the
conversion of the reaction is 95-100% (as measured by .sup.1H
NMR).
[0049] Imine Reduction
[0050] This invention provides a process for the chemical reduction
of the imine (Formula IV) to the reduced form (Formula V), as
illustrated in Scheme 6. 8
[0051] As shown, a metal hydride reducing agent is reacted with a
metal salt or an organic acid in an organic solvent to generate a
reducing agent. Then, the imine solution is added to the reducing
agent, which leads to the reduction of the imine.
[0052] Examples of metal hydride reducing agents are sodium
borohydride, lithium aluminum hydride, sodium
triacetoxyborohydride, sodium cyanoborohydride and lithium
borohydride with the preferred reagent being sodium
borohydride.
[0053] Examples of metal salts are zinc chloride, potassium
hydroxide, sodium hydroxide and sodium acetate, with zinc chloride
being the preferred reagent.
[0054] Examples of organic acids are formic acid, oxalic acid,
citric acid, acetic acid and propionic acid, with acetic acid being
the preferred reagent.
[0055] Reaction of the borohydride with the metal salt or organic
acid is done in an organic solvent, examples of which include, but
are not limited to, diethyl ether, dimethoxyethane,
tetrahydrofuran, dichloromethane, benzene and toluene. A preferred
solvent is tetrahydrofuran. The reaction is usually performed at a
reduced temperature, typically between -40.degree. C. and 0.degree.
C., with a preferred temperature being in the -25 to -5.degree. C.
range. Reaction yields range from 65-90%, with a typical yield for
the zinc chloride/sodium borohydride method being approximately
80%.
[0056] Alkylation Process
[0057] This invention provides a process for the alkylation of the
secondary amine (Formula V) with an amine-protected
2-chloromethylbenzimidazole (Formula VI) to synthesize the tertiary
amine according to Formula VII. More particularly, Scheme 7 depicts
the reaction of the secondary amine (Formula V) with the
amine-protected 2-chloromethylbenzimidazole (Formula VI) in an
organic solvent at elevated temperature in the presence of an amine
base and a catalytic amount of an iodide. (See also, Cook et al.,
Tetrahedron, 54:3999-4012 (1998)). 9
[0058] As shown, the Formula VI compound bears a butoxycarbonyl
amine protecting group. It should be readily apparent that other
amine protecting groups are also useful in the practice of the
present invention and could be easily substituted for the
butoxycarbonyl group and thereafter removed using known methods.
Examples of other protecting groups include, but are not limited
to, methoxycarbonyl, benzyl, benzyloxycarbonyl, allyl,
toluenesulfonyl, methanesulfonyl, and acetyl.
[0059] The reaction is typically carried out with a stoichiometric
excess of the Formula VI compound. In particular, the reaction is
generally carried out with 1.0 to 2.0 equivalents of the Formula VI
compound (compared to the Formula V compound) with a preferred
range being 1.05-1.15 equivalents.
[0060] A number of amine bases have been used in the reaction,
including but not limited to, triethylamine and
diisopropylethylamine, with the preferred reagent being
diisopropylethylamine. Other amines which are applicable include
tetramethylguanidine, 1,8-diazabicyclo[5.4.0]undec-7-e- ne and
1,4-diazabicyclo[2.2.2]octane. Typically, 1.1 to 1.5 equivalents of
the amine base relative to the amine V are used.
[0061] Solvents for the reaction include dichloromethane,
chloroform, tetrahydrofuran, dimethylformamide, benzene, toluene
and acetonitrile with acetonitrile being a preferred solvent.
Reaction temperatures range from ambient to reflux, with an ideal
range being 50-60.degree. C.
[0062] A catalytic amount (0.01 to 0.2 equivalents) of an iodide
source, such as potassium iodide, cesium iodide, sodium iodide or
tetrabutylammonium iodide is typically added to increase the
reaction rate. The typical yield of the Formula VII compound for
the reaction is 80-95%.
[0063] Amine Protecting Group Removal
[0064] Furthermore, this invention provides procedures for the
removal of the butoxycarbonyl protecting group, if present, and the
phthalimide amine protecting groups from the Formula VII compound.
Scheme 8 illustrates the procedures for deprotection. 10
[0065] In a preferred embodiment, the benzimidazole amine
t-butoxycarbonyl protecting group is selectively hydrolyzed under
acidic aqueous conditions to generate the Formula VIII compound.
Subsequently, the primary amine phthalimide protecting group of the
Formula VIII compound is then hydrolyzed in an organic solvent with
hydrazine or another amine-based reagent. Thereafter, the
deprotected compound according to Formula I, which is free of
hydrazine and other side products, including hydrazide IX, can be
isolated.
[0066] The removal of the butoxycarbonyl protecting group from the
Formula VII compound can be accomplished under standard conditions
using aqueous acidic media. A number of acids can be employed, such
as hydrochloric acid, sulfuric acid, acetic acid, trifluoroacetic
acid, 4-toluenesulfonic acid, methanesulfonic acid and propionic
acid. A preferred condition is aqueous hydrochloric acid (pH 2-3).
The conversion to the Formula VIII compound is very efficient,
typically 95% yield or more. Upon completion of the reaction, which
typically takes 12-16 hours and can be monitored by HPLC, the pH of
the solution is raised through the addition of a base such as 10%
aqueous sodium hydroxide to about a pH of 10-12, and the mixture is
extracted into an organic solvent such as dichloromethane.
[0067] The removal of the phthalimide protecting group from the
Formula VIII compound can be accomplished under standard conditions
using a number of different reagents including, but not limited to
ammonia, methylamine, butylamine, ethylenediamine, hydrazine
hydrate and sodium borohydride followed by acetic acid. A preferred
reagent is hydrazine hydrate. Typically, about 8-10 equivalents of
hydrazine hydrate are used. Solvents for the reaction include
methanol, ethanol, isopropanol, ethylene glycol, dimethylformamide
and tetrahydrofuran. The reaction is carried out at ambient
temperature or at elevated temperature (reflux), at 50-100 C,
solvent dependant. Generally, the reaction times are on the order
of 12-24 hours at ambient temperature. Removal of the hydrazide
side product (i.e., the Formula IX compound) can be accomplished
through filtration. The filtration of the hydrazide side product
can be made more efficient through the addition of an organic
solvent such as dichloromethane to the reaction mixture to aid in
the complete precipitation of the Formula IX compound from
solution.
[0068] Although sequential removal of the amine protecting groups
is exemplified, it should be apparent to one of skill in the art
that a benzimidazole amine protecting group can be selected which
can be removed simultaneously with the phalamide amine protecting
group.
[0069] Optional Decolorizing and Purification Procedures:
[0070] This invention also provides optional additional steps for
the purification and/or decolorization of the Formula I compound as
follows. In one example, an aqueous solution of the compound having
Formula I may be treated with decolorizing carbon to remove colored
impurities. In another example, the compound having Formula I may
be extracted using an organic solvent, and purified using silica
gel flash chromatography.
[0071] The Formula I compound in freebase form, in a mixture of
dichloromethane and another solvent can be washed with an aqueous
base such as 0.5N sodium hydroxide to remove traces of hydrazine.
The Formula I compound can then be extracted into a dilute aqueous
acid such as 1N hydrochlororic acid. The Formula I compound is
readily soluble in aqueous media at a pH at or below 6.0. If the pH
of the aqueous solution is below 5, it can then be adjusted to 5-7,
with a preferred pH being 6.0 for the removal of impurities.
Non-polar organic impurities will remain in the organic layer. A
number of solvents can be used, if desired, for further extraction
of non-polar organic impurities including ethyl acetate, methyl
t-butyl ether, tetrahydrofuran, dichloromethane and chloroform.
[0072] If a decolorizing procedure is desired, activated charcoal
can be added to the aqueous solution. Typically, 10 to 30 weight %
carbon is used (relative to the amount of compound I), and the
mixture is stirred for 3-16 hours. A typical procedure uses 20
weight % activated carbon in pH 6 aqueous for 8 hours. The mixture
is then filtered to remove the carbon. A number of alternative
varieties of activated carbon can be used, including, but not
limited to Darco.RTM. G-60, Darco.RTM. KB or Norit.RTM. (registered
trademark of Norit Americas Inc. Marshall, Tex.).
[0073] Alternatively, the decolorizing carbon treatment can be
applied to the filtered reaction mixture comprising compound I,
after the washes with aqueous base and prior to extraction into
aqueous acid. Solubilization of the Formula I compound in other
organic solvents, such as methanol, ethanol or isopropanol,
followed by decolorizing carbon treatment can alternatively be
conducted.
[0074] In order to extract the Formula I compound into organic
media, the pH of the aqueous solution can be increased to about
11-12 through the addition of an aqueous base, such as 10% sodium
hydroxide. The freebase Formula I compound can then be extracted
into an organic solvent such as dichloromethane, chloroform or
toluene, with dichloromethane being a preferred solvent.
[0075] If desired, the solution can be passed through a column,
which has been pre-treated with an organic solvent mixture. The
column can consist of florisil, silica gel or alumina, with silica
gel being a preferred solid phase. Typically, 0.5 to 10 weight
equivalents of silica gel (relative to compound I) are employed in
the purification, with 0.5-2.0 weight equivalents being preferred.
Typically, 240-400 mesh, 60 .ANG. column chromatography grade
silica gel is used. The elution of the compound can be achieved in
fractions, by using a mixture of alcohol and chlorinated organic
solvents such as methanol and dichloromethane. In one example, the
eluent is a mixture of 79% dichloromethane, 20% methanol and 1%
concentrated aqueous ammonium hydroxide (by volume). The elution
can be followed by sampling the eluted fractions, and analyzing by
thin layer chromatography, using procedures that would be familiar
to those with skill in the art.
[0076] Following the silica gel column, the combined fractions
containing compound I in organic media are typically washed once
with a dilute inorganic base such as 1 N sodium hydroxide to ensure
that the material is completely freebased. Following the wash, the
organic fractions are dried with an anhydrous desiccant such as
anhydrous magnesium sulfate or anhydrous sodium sulfate.
[0077] Optional Crystallization
[0078] For synthetic routes initiated with an optically active
Formula II compound, and therefore providing an optically active
Formula I compound, this invention provides a process for the
crystallization of the Formula I compound from a mixture of organic
solvents. In one example, the invention provides a process for
making an optically active compound having Formula I,
comprising:
[0079] a) concentrating a solution containing a compound having
Formula I in a mixture of organic solvents (solvent A), to form a
solution with a predetermined concentration;
[0080] b) adding a suitable crystallization solvent or mixture of
solvents (solvent B) to the solution in a), and optional removal of
the residual solvent A by a co-distillation process to a
predetermined volume or concentration at a specified
temperature;
[0081] c) seeding the solution in b) at an appropriate temperature
with a small amount of pure crystalline Formula I compound (of the
appropriate enantiomeric form), and cooling the mixture with
agitation under controlled conditions such that crystals having
Formula I are spontaneously formed; and
[0082] d) filtering and drying crystalline material.
[0083] The concentration of the Formula I compound solution is
generally conducted under vacuum, where the primary solvent A can
be easily and quickly removed to a predetermined volume, typically
about 500 mg/mL. If desired, the solution can be concentrated to
dryness. In one example, solvent A comprises dichloromethane. A
typical residual dichloromethane level if the mixture is
concentrated to dryness, under approximately 25 mmHg vacuum, would
be on the order of 30 mole % relative to the Formula I
compound.
[0084] A crystallization solvent (solvent B) is then added which
can include, but is not limited to the following, or mixtures of
the following: tetrahydrofuran, ethyl acetate, cumene, isopropyl
acetate, n-propyl acetate, dichloromethane, ethanol, isopropanol,
methanol, isopropyl ether, diethyl ether and t-butyl methyl ether.
A preferred solvent is isopropyl acetate. A sufficient volume of
solvent B is added to typically reach a complete solvation of
compound I at an elevated temperature. The elevated temperature
will depend on the nature of the solvent, with a reflux condition
being the highest temperature possible. As an example, in the case
of isopropyl acetate, it is possible to achieve complete solubility
with concentration of compound I of approximately 125 mg/mL at a
temperature of 60-65.degree. C.
[0085] At this point, if desired, the solution can be placed under
vacuum, and concentrated. During the concentration process, which
can be conducted at ambient or elevated temperatures, the level of
solvent A in the solution can be monitored by .sup.1H NMR
measurements. The concentration of solvent A can therefore be
controlled during the co-distillation process. In the case of
dichloromethane (solvent A) in isopropyl acetate (solvent B), a
level of less than 2 mol % of solvent A is preferred.
[0086] The concentration is then typically carried out to a
predetermined final concentration, at which point the Formula I
compound is saturated or supersaturated. In the case of isopropyl
acetate, a concentration of between 100 and 200 mg/mL is used, with
125 mg/mL being a preferable level. At this point, the mixture is
allowed to cool, with agitation. Generally, a small amount of
crystalline Formula I compound is added to the solution to "seed"
the crystallization process. The crystals will spontaneously begin
to form upon cooling. Isolation of the crystalline material is
possible through filtration.
[0087] The yield of crystalline material depends on the solvent
mixtures used. For a concentration of 125 mg/mL of the Formula I
compound in isopropyl acetate, the yield of crystalline material is
typically 75%, and is isolated as a fine white to pale yellow
powder. In order to reduce the levels of residual solvents on or in
the crystalline material, the crystalline Formula I compound is
typically dried in a 40.degree. C. vacuum oven (2-5 mmHg vacuum)
for 24 hours or more.
[0088] The following examples are intended to illustrate, but not
to limit, the invention.
EXAMPLE 1
Synthesis of
(N'-(1H-benzimidazol-2-ylmethyl)-N'-5,6,7,8-tetrahydroquinoli-
n-8-yl-1,4-butanediamine from a Phthalimide-Substituted Alkyl
Aldehyde
Preparation of (S)-8-amino-5,6,7,8-tetrahydroquinoline freebase
(II) from amine Salt
[0089] 11
[0090] (S)-8-amino-5,6,7,8-tetrahydroquinoline hydrochloride (23.4
kg, 106 mol) was dissolved in deionized water (60 L) and
neutralized to pH 7 with a 50% sodium hydroxide solution
(.about.11.5 kg). The mixture was extracted with dichloromethane
(126 kg). The pH of the aqueous layer was re-adjusted to 7 with 50%
NaOH, and was extracted again with dichloromethane (126 kg). The
dichloromethane fractions are then discarded. The pH of the aqueous
layer was increased to 13 with 50% NaOH. The aqueous layer was then
extracted with dichloromethane (2.times.126 kg). The combined
organic layers were dried (sodium sulfate) and concentrated in
vacuo to afford (S)-8-amino-5,6,7,8-tetrahydroquinoline (12.7 kg,
81% yield, purity: 96% by HPLC) as a dark brown oil. .sup.1H NMR
(CDCl.sub.3) .delta. 1.64-1.84 (m, 2H), 1.94-2.01 (m, 1H),
2.14-2.23 (m, 1H), 2.69-2.87 (m, 2H), 3.99 (dd, 1H, J=7.7, 5.3 Hz),
7.06 (dd, 1H, J=7.7, 4.4 Hz), 7.36 (d, 1H, J=7.5 Hz), 8.41 (d, 1H,
J=4.4 Hz).
[0091] Chiral purity determined by gas chromatography to be 97.5%
ee (separated by chiral GC, J&W CycloSil B column, isothermally
run at 130.degree. C. for 40 min., (S)-(+)-enantiomer.sub.rt=26.3
min, (R)-(-)-enantiomer.sub.rt=28.7 min).
[0092] Imine Formation (IV) with K.sub.2CO.sub.3 in THF: 12
[0093] To a solution of 8-amino-5,6,7,8-tetrahydroquinoline (12.7
kg, 85.8 mmol, 1.0 eq.) in THF (50 L) was added
4-(1,3-dioxo-1,3-dihydroisoindol-2- -yl)butan-1-al (15.8 kg, 72.8
mmol, 0.8 eq) and 325 mesh potassium carbonate (11.8 kg, 85.8 mol,
1.0 eq). The mixture was then stirred for 2 hours. A proton NMR of
an aliquot from the sample was used to determine stoichiometry.
Based on the calculation, another 0.18 eq of aldehyde (15.4 mol,
3.35 kg) was added. After stirring for 2 hours, a second proton NMR
aliquot showed complete and clean imine IV formation (>97%
conversion). .sup.1H NMR (CDCl.sub.3) .delta. 1.76-2.19 (series of
m, 6H), 2.35 (m, 2H), 2.78 (m, 2H), 3.73 (m, 2H), 4.31 (t, 1H,
J=5.1 Hz), 7.05 (dd, 1H, J=7.8, 4.8 Hz), 7.38 (d, 1H, J=7.8 Hz),
7.69 (m, 2H), 7.80 (m, 2H), 7.82 (t, 1H, J=4.1 Hz), 8.38 (d, 1H,
J=4.8 Hz). The mixture was then filtered.
[0094] Generally, sometrically equal amount of the amine II and the
aldehyde III are used in the imine formations, with an equimolar
amount of dehydrating agent (if used). Alternatively, imines may be
formed without a dehydrating agent using THF, dichloromethane, or
methanol. Imines may also be formed using dimethoxyethane or
diethyl ether as the solvent and K.sub.2CO.sub.3 as the dehydrating
agent. Alternatively, imines may be formed using dichloromethane as
the solvent and MgSO.sub.4 as the dehydrating agent. These
alternative conditions for forming imines gave a >80% conversion
to the imine as measured by NMR.
[0095] Reduction of Imine Using Acetic Acid/Sodium Borohydride
13
[0096] Reagent formation: To a mechanically stirred -20.degree. C.
(internal temperature) suspension of powdered sodium borohydride
(15.3 g, 400 mmol, 1.2 eq.) in THF (1700 mL) in a 5 L flask was
added glacial acetic acid (36.2 mL, 633 mmol, 1.9 eq.) in a
dropwise manner over 15 minutes. An effervescence occurred upon
addition, which subsided after approximately 5-10 minutes following
the completion of addition. The mixture was then stirred until it
became homogeneous and translucent (60 minutes), and was then
cooled to -20.degree. C.
[0097] The filtered imine IV (338 mmol in 1.7 L THF) was then
cooled to -20.degree. C. (internal temperature), and was added over
15 minutes to the -20.degree. C. borohydride mixture via cannula.
Following addition, the reaction was stirred, at a temperature of
between -15 and -20.degree. C. Aliquots of the reaction mixture
were taken at 15 minute intervals, starting at a stirring time of
30 minutes. The reaction was determined to be complete at 75
minutes stirring time, as measured by proton NMR.
[0098] Work-up procedures involve quenching the reaction, removing
impurities, and recovering the product. The reaction was quenched
with saturated aqueous sodium bicarbonate at -20.degree. C. (700
mL), and was allowed to warm for 15 minutes. Dichloromethane (3 L)
was then added and the aqueous and organic layers were separated.
The organic layer was extracted two more times with dichloromethane
(1.5 L fractions). If the sodium bicarbonate precipitates upon
addition to the reaction (after warming), sufficient distilled
water is added to ensure homogeneity of the aqueous layer. In this
example, 300 mL water was added.
[0099] To remove impurities, the combined dichloromethane fractions
are concentrated, and the residue is taken up in 5% aqueous acetic
acid (1.2 L). The aqueous layer is washed once with hexanes (1.5
L). The hexanes layer is washed with a small amount of water. The
combined aqueous fractions are then washed twice with methyl
t-butyl ether (2.times.600 mL fractions). Separation of aqueous and
organic layers during the MTBE extractions may take 10-15 minutes.
Generally, the more complete the separation, the more efficient the
impurity removal process will be.
[0100] To recover the product, solid sodium bicarbonate is slowly
added to the well-stirred aqueous layer to bring the pH to 7
(measured by pH paper). If there is still a residual amount of MTBE
remaining, it is separated at this stage from the aqueous layer.
The aqueous layer is extracted three times with dichloromethane
(3.times.1 L fractions). The combined dichloromethane fractions
were then washed with saturated aqueous sodium bicarbonate (300
mL--to remove residual acetic acid), separated, dried over
anhydrous magnesium sulfate, filtered and concentrated to afford
the desired product, which was isolated as a pale foam in a yield
of 92.3 g (74%). .sup.1H NMR (CDCl.sub.3) .delta. 1.59-2.17 (series
of m, 8H), 2.74 (m, 4H), 3.72 (t, 2H, J=7.2 Hz), 3.72 (m, 1H), 7.04
(dd, 1H, J=7.8, 4.8 Hz), 7.35 (dd, 1H, J=7.8, 0.6 Hz), 7.70 (m,
2H), 7.82 (m, 2H), 8.36 (dd, 1H, J=4.8, 0.6 Hz). ES-MS m/z 350
(M+H); Purity by HPLC: 90.9%. Chiral purity 97% ee (by chiral
HPLC).
[0101] Reduction of Imine Using Zinc Chloride/Sodium Borohydride:
14
[0102] First, the reducing agent is formed, followed by reduction
of the imine, and work-up. To a reactor containing THF (80 L) was
added zinc (II) chloride (12.8 kg, 94.3 mol). A mild exothermic
occurs upon dissolution. Sodium borohydride (3.24 kg, 85.8 mol) is
then added slowly. The mixture is then stirred for one hour, during
which time a homogeneous solution is formed. The solution is then
cooled to -15.degree. C.
[0103] A solution of imine IV (85.8 mmol) in THF (50 L) was cooled
to -20.degree. C., and was added slowly to the cooled solution of
zinc chloride and sodium borohydride, maintaining the internal
temperature of the reaction flask between -7 and -15.degree. C. The
reaction was then stirred at -15.degree. C. for 3 hours. At this
point, an in-process HPLC determined that the reaction was
complete.
[0104] For work-up, a solution of 6N aqueous HCl (35 L) was slowly
added, maintaining the temperature below -5.degree. C., until the
pH of the aqueous layer measured 2-3. The reaction was allowed to
warm to room temperature, then a solution of 13% aqueous sodium
carbonate (12 L) was added until the pH reached 4. The reactor was
placed under vacuum, and the THF solvent was removed by
distillation. Water (120 L) and dichloromethane (160 L) were then
added. The mixture was then agitated, and then the aqueous and
organic layers were separated. The organic layer was then washed
with concentrated aqueous ammonium hydroxide (100 L) and then water
(60 L). The dichloromethane solution was then passed through a 20
kg pad of silica gel. The dichloromethane solution was then
concentrated under vacuum, then diisopropyl ether (50 L) was added.
The solution was then concentrated under vacuum, and was then
cooled slowly to -10.degree. C., with agitation, during which time,
a precipitate formed. The precipitate (desired amine V) was
filtered, and washed with diisopropyl ether. After drying under
vacuum, the desired product V was obtained in a 20.4 kg yield (65%,
corrected for solvent and purity) as a light brown crystalline
solid. Purity by HPLC 95%.
[0105] Alkylation with Carbamate Cleavage in Work-up 15
[0106] To a reactor was charged amine V (9.9 kg, 28.6 mol),
benzimidazole VI (8.0 kg, 30.0 mol) and potassium iodide (144 g,
0.86 mol). A solution of diisopropylethylamine (6.0 L, 34.3 mol) in
anhydrous acetonitrile (60 L) was then added. The mixture was
stirred, and the flask was warmed to a 50.degree. C. internal
temperature. The temperature was maintained for 200 minutes, at
which point, an NMR aliquot determined that the reaction was
complete. The reaction was then cooled, and the solvent was removed
under vacuum (25 mmHg). The residue was then suspended in water (50
L), and 4N aqueous HCl (.about.15 L) was added slowly until a pH of
2 was reached. The aqueous layer was then extracted twice times
with 40 L portions of methyl t-butyl ether (which were discarded).
The aqueous layer was then stirred for 16 hours at ambient
temperature. Toluene (60 L) was then added, and a 3N aqueous NaOH
solution was added until the pH of the aqueous layer reached 11.
The layers were then separated. The organic layer was then dried
over anhydrous sodium sulfate. The solution was then filtered and
stored at 3.degree. C. or below as a stock solution. An aliquot of
the solution was concentrated, and the purity of the product VIII
was determined to be 91% by HPLC. The yield was determined, by
concentration of a representative aliquot to dryness, to be 83%
(11.3 kg of VIII in the stock solution). .sup.1H NMR (CDCl.sub.3)
.delta. 1.20-1.50 (m, 2H), 1.60-1.80 (m, 1H), 1.85-2.10 (m, 2H),
2.45-2.65 (m, 3H), 2.65-2.95 (m, 3H), 4.00 (d, 1H, J=16.8 Hz), 4.07
(m, 1H), 4.12 (d, 1H, J=16.8 Hz), 7.10-7.30 (m, 4H), 7.42 (d, 1H,
J=7.5 Hz), 7.55 (br s, 1H), 8.59 (d, 1H, J=4.4 Hz). ES-MS m/z 480
(M+H).
[0107] Phthalimide Deprotection with Decolorizing Treatment and
Selective Extraction of I 16
[0108] The toluene stock solution of VIII (94 kg, containing 11.3
kg of VIII, 23.9 mol, corrected for purity) was concentrated under
reduced pressure to remove most of the toluene. The oily residue
was dissolved in methanol (25 L) and hydrazine hydrate (14 kg,
.about.230 mol (N.sub.2H.sub.4.1.5H.sub.2O)) was then added. The
solution was stirred mechanically at room temperature for 17 h. The
phthalylhydrazide was removed by filtration and the filtrate was
concentrated under reduced pressure. Dichloromethane (20 L) was
added and the solution was washed with a 0.5N NaOH solution
(2.times.30 L). The organic and aqueous phases were separated and
water (20 L) was then added. 3N HCl was then added to bring the pH
to 5-6. The aqueous and organic phases were separated, and the
aqueous phase was treated with activated carbon (Norit G-60, 3 kg)
for 16 h. The mixture was filtered and the pH of the filtrate was
adjusted to 12 with 3N NaOH. The resulting solution was extracted
with dichloromethane (50 L). The pH of the aqueous phase was
re-adjusted to 12 with 3N NaOH and was extracted with a second
portion of dichloromethane (50 L).
[0109] The combined organic fractions were loaded on to a silica
gel column (12 kg) and the product was then eluted using a 79:20:1
dichloromethane/methanol/ammonium hydroxide solution. In this
example, the silica gel was pre-conditioned with the eluent prior
to loading the compound. A series of 50 L fractions were collected,
and analyzed by TLC. The pure fractions were collected (3
fractions) and the total volume was concentrated to 20 L. The
residue was dissolved in dichloromethane (60 L) and washed with
1.25 N NaOH (30 L). The organic phase was then dried with anhydrous
Na.sub.2SO.sub.4 and filtered to afford compound I
(N'-(1H-benzimidazol-2-ylmethyl)-N'-(5,6,7,8-tetrahydro-quinolin-8-yl)-bu-
tane-1,4-diamine) as a dichloromethane solution (4.5 kg, 56%, 98%
pure by HPLC, 98% e.e.). .sup.1H NMR (CDCl.sub.3) .delta. 1.23-1.49
(m, 4H), 1.62-1.77 (m, 1H), 1.85-1.97 (m, 1H), 2.00-2.10 (m, 1H),
2.16-2.26 (m, 1H), 2.51 (t, 2H, J=6.8 Hz), 2.54-2.62 (m, 1H),
2.67-2.78 (m, 1H), 2.81-2.92 (m, 1H), 7.15 (d, 1H, J=7.6 Hz),
7.18-7.23 (m, 2H), 7.59 (br s, 1H), 8.60 (d, 1H, J=4.4 Hz). ES-MS
m/z 350 (M+H).
[0110] Crystallization of Compound I
[0111] Compound I may be crystallized as a free base using
isopropyl acetate solvent, with co-distillation removal of
dichloromethane. A solution of I (4.5 kg, 12.9 mol) in
CH.sub.2Cl.sub.2 (50 L) was stirred with anhydrous Na.sub.2SO.sub.4
(500 g, 3.5 mol) for 8 hours at room temperature. The mixture was
filtered and transferred into a reactor and the solution was placed
under an atmosphere of nitrogen. The mixture was warmed to
25.degree. C. and placed under vacuum (approximately 30 mmHg) to
remove the CH.sub.2Cl.sub.2, maintaining the temperature of the
solution between 20.degree. C. and 30.degree. C. during the
concentration. Isopropyl acetate (32 L) was then added.
[0112] A proton NMR aliquot showed a dichloromethane content of
.about.9 mol % relative to isopropyl acetate. The mixture was
placed under vacuum again, and was concentrated to a volume of
.about.15 L, maintaining an internal temperature of less than
40.degree. C. A second portion of isopropyl acetate (17 L) was
added and the solution was concentrated to .about.15 L, keeping the
internal temperature between 30 and 40.degree. C. An aliquot of the
solution showed a residual dichloromethane level (relative to
isopropyl acetate) to be less than 1 mol % by .sup.1H NMR.
[0113] The vacuum was then released, and the mixture was placed
under a nitrogen atmosphere, and was heated to 65.degree. C. At
this point, the material was soluble, and was allowed to cool to
50.degree. C., at which point, 100 g of crystalline I was added.
The solution was allowed to cool slowly to room temperature (over 8
h) with stirring. During this time, crystals of compound I formed
as a fine, off-white powder. The mixture was filtered through a
fritted glass funnel (with vacuum) and the solids were washed with
cold (.about.5.degree. C.) isopropyl acetate (100 mL). The crystals
were dried under vacuum (2 mm Hg, 40.degree. C.) for 24 h to afford
I as a fine off-white powder (3.0 kg, 67%). Achiral purity: 99%
(HPLC). Chiral Purity: >99% ee. Residual solvents (GC) Isopropyl
Acetate, 3700 ppm; dichloromethane, 31 ppm.
[0114] In an alternative crystallization procedure, compound I (1.1
kg) was transferred to a 20 L flask, to which isopropyl acetate (10
L) was added. The flask was heated slowly to an internal
temperature of 67.degree. C., at which point all the solids had
dissolved and the resulting solution was transparent. The solution
was then cooled slowly to 50.degree. C., with agitation, and was
seeded with 10 g of crystalline compound I. The mixture was then
cooled to ambient temperature with agitation, during which time the
compound I precipitated as fine crystals. The flask was cooled to
0.degree. C., and the slurry was filtered, washing with 0.degree.
C. isopropyl acetate (1 L). The crystalline compound I was then
dried in a 40.degree. C. vacuum oven (27 mm Hg) for 24 hours to
give 820 g (75%) yield of crystalline material.
[0115] The crystalline compound I may also be isolated from a
number of different solvent systems. Compound I is soluble at
>600 mg/mL in 55.degree. C. tetrahydrofuran, and can be
recovered as crystalline material by cooling the solution.
Similarly, compound I can be isolated as crystalline material from
a hot solution of cumene. Compound I is very soluble in
dichloromethane (>700 mg/mL), but can be precipitated as a
crystalline material from the solution through the addition of
diethyl ether. Ethyl acetate is an effective solvent for
crystallization, with solubilities of compound I of ca. 150 mg/mL
at 60.degree. C. being achievable.
EXAMPLE 2
Synthesis of
(N'-(1H-benzimidazol-2-ylmethyl)-N'-5,6,7.8-tetrahydroquinoli-
n-8-yl-1,4-butanediamine from a tert-butoxycarbonyl (BOC)
substituted alkyl aldehyde
Preparation of N,N-Di-tert-butoxycarbonylaminobutyraldehyde
Synthesis (Formula IIIa)
[0116] 17
[0117] Aminoacetal A (133.19 g, 1.0 mol) was dissolved in
dichloromethane (300 mL) and cooled in an ice-water bath. When
internal temperature had dropped below 2.degree. C., a solution of
Boc.sub.2O (218.25 g, 1 eq.) in dichloromethane (200 mL) was added
via a pressure-equalizing dropping funnel. The addition was kept at
such a rate that the internal temperature remained below 10.degree.
C. After the addition, the cold bath was removed and the mixture
was stirred at room temperature for 30 min. An aliquot was removed
via a syringe and dried under high vacuum. NMR of the residue
indicated completed and clean reaction. All volatiles were removed
by rotary evaporation and the residue was further dried on high
vacuum for 1 hour at 50.degree. C. with stirring to give
tert-butylcarbonylbutyraldehyde dimethyl acetal B in quantitative
yield. .sup.1H NMR (.delta., CDCl.sub.3): 4.61 (s, br, 1 H), 4.37
(t, J=5.4 Hz, 1 H), 3.32 (s, 6 H), 3.19-3.07 (m, 2 H), 1.68-1.50
(m, 4 H), 1.44 (s, 9 H) ppm.
[0118] Compound B from the above reaction was dissolved in
anhydrous THF (700 mL) and cooled in an ice-water bath. When the
internal temperature was below 4.degree. C., i-PrMgCl (2.0 M in
THF, 550 mL, 1.1 eq.) was added slowly via a pressure equalizing
dropping funnel at a rate that kept the temperature at
5.+-.2.degree. C. The dropping funnel was rinsed with .about.50 mL
THF. The mixture was stirred in the cold bath for 20 min after the
Grignard addition, and then a solution of Boc.sub.2O (218.25 g, 1
eq.) in THF (200 mL) was added slowly that kept the temperature at
5.+-.2.degree. C. After 30 minutes, TLC and NMR confirmed clean and
complete reaction. The reaction was quenched cold by drop-wise
addition of aqueous HCl (6 M, 150 mL). Celite (66 g) and anhydrous
MgSO.sub.4 (67 g) were added. The mixture was stirred for 5 minutes
and then filtered through a celite pad (1 cm celite on a 600 mL
sintered glass funnel). The filtrate was concentrated to dryness to
give di-tert-butylcarbonylbutyraldehyde dimethyl acetal C in
quantitative yield. .sup.1H NMR (.delta., CDCl.sub.3): 4.37 (t,
J=5.2 Hz, 1 H), 3.58 (t, J=7.01 Hz, 2 H), 3.31 (s, 6 H), 1.65-1.59
(m, 4 H), 1.50 (s, 18 H) ppm.
[0119] Crude C from above (.about.1 mol) was dissolved in THF (400
mL) and the solution was added to a mixture of HOAc (glacial, 1.5
L) and water (0.9 L). The mixture was stirred at room temperature
for 24 h. All volatiles were removed by rotary evaporation under
high vacuum (bath 45 .degree. C.), and the residue was partitioned
between water (600 mL) and hexane (400 mL) at room temperature. The
pH of the aqueous layer was adjusted to .gtoreq.10 by 4M NaOH while
cooled in a cold-water bath (total 370 mL added). The aqueous was
extracted with hexane (500 mL.times.2); the combined organic layers
were washed once with saturated NaHCO.sub.3 (600 mL) and dried with
anhydrous MgSO.sub.4 (100 g). The mixture was filtered through a
silica pad (2 cm silica on a 600 mL sintered glass funnel) and the
filter cake was rinsed with 200 mL of 4:1 hexane-ether. The
filtrate was concentrated by rotary evaporation and further dried
under high vacuum with stirring for 1 h to give
di-tert-butylcarbonylbutyraldehyde (IIIa) as light yellow oil
(222.44 g, 77.5% over 3 steps, 93% LC purity and 0.064% water
content). .sup.1H NMR (.delta., CDCl.sub.3): 9.78 (t, J=1.4, 1 H),
3.62 (t, J=7.1 Hz, 2 H), 2.47 (td, J.sub.1=7.4 Hz, J.sub.2=1.2 Hz,
2 H), 1.91 (quent., J=7.29 Hz, 2 H), 1.51 (s, 18 H) ppm; MS (M/z):
310, 210.
[0120] Reductive Amination 18
[0121] A 2 L, 3-neck round bottom flask was fitted with a
mechanical stirrer, a thermometer, and a pressure-equalizing
dropping funnel. (S)-8-amino-5,6,7,8-tetrahydroquinoline (II)
(120.61 g, 0.81 mol) was dissolved in THF (400 mL) under N.sub.2.
Anhydrous K.sub.2CO.sub.3 (110 g, 0.80 mol) was added and the
mixture was cooled in an ice-water bath.
Di-tert-butylcarbonylbutyraldehyde (IIIa) (247.74 g, 0.80 mol) was
dissolved in THF (200 mL) and added to the reaction mixture via the
dropping funnel at such a rate to maintain the internal temperature
below 5.degree. C. The dropping funnel was rinsed with THF (100 mL
in 2 portions). The cold bath was removed and the mixture was
allowed to stir at room temperature until an aliquot NMR indicated
complete imine formation. To avoid false completion results, a drop
of reaction mixture was diluted with CDCl.sub.3, and NMR was taken
directly. Furthermore, the integration of .delta. 8.39 peak was
calibrated to 1, so the aldehyde (.delta. 9.77, s) peak should be
.ltoreq.0.05 and imine (.delta. 7.88, t) should be .gtoreq.0.95.
The imine solution was filtered through a pad of celite (5 mm
celite on a 300 mL sintered glass funnel) under a N.sub.2 blanket
and held under N.sub.2. .sup.1H NMR (.delta., CDCl.sub.3): 8.40 (m,
1 H), 7.90 (t, J=4.7 Hz, 1 H), 7.40 (d, J=7.7 Hz, 1 H), 7.07 (dd,
J.sub.1=7.7 Hz, J.sub.2=4.7 Hz, 1 H), 4.32 (t, J=5.4 Hz, 1H), 3.62
(td, J.sub.1=7.4 Hz, J.sub.2=3.0 Hz, 2 H), 2.95-2.70 (m, 2 H),
2.36-2.28 (m, 1 H), 2.06-1.98 (m, 3 H), 1.86-1.66 (m, 2H,
overlapped with THF signal), 1.49 (s, 18 H) ppm.
[0122] In a second reaction vessel, anhydrous ZnCl.sub.2 (166 g,
1.5 eq.) was added in portions to THF (800 mL) while cooled in a
dry ice/acetone/water bath (.ltoreq.-20.degree. C.). The rate of
addition was controlled to maintain internal temperature at
0.about.8.degree. C. When all ZnCl.sub.2 had dissolved, solid
NaBH.sub.4 (31 g, 1 eq.) was added portion-wise to obtain a
slightly turbid solution. The resulting mixture was cooled to
-40.degree. C. and the imine solution was introduced slowly while
maintaining the internal temperature below -20.degree. C. After the
imine addition, the reaction mixture was stirred at -20.degree. C.
for 30 minutes, when NMR of an aliquot sample indicated completed
reduction. To obtain an aliquot sample for NMR, an aliquot was
withdrawn from the reaction vessel and quenched with saturated
NH.sub.4Cl solution. The mixture was extracted with
dichloromethane, and the organic layer dried under high vacuum,
yielding a residue which was checked by NMR.
[0123] Saturated NH.sub.4Cl aqueous solution ({fraction (1/10)} of
total volume) was added dropwise at -20.degree. C. After the
addition, the reaction mixture was warmed up to room temperature
while aqueous HCl (3 M) was added to bring the aqueous pH to
.about.5. The mixture was stirred for 2 hours at room temperature,
and then it was partitioned between water (6 L) and dichloromethane
(2 L). Saturated NH.sub.4Cl solution (500 mL) and concentrated
NH.sub.3.H.sub.2O (500 mL) were added and the mixture was
vigorously stirred for 20 min. The organic layer was drained and
the aqueous layer was re-extracted with dichloromethane (2 L). The
organic layer was combined and the aqueous was discarded.
[0124] The organic extract was washed once with a mixture of
saturated NH.sub.4Cl (500 mL), concentrated NH.sub.3.H.sub.2O (500
mL), and water (2 L), and once with water (3 L). The organic layer
was then stirred with water (2 L) and the pH of the equilibrated
aqueous was adjusted to 2 by dilute HCl (1 M). The dichloromethane
layer was separated and dried with anhydrous MgSO.sub.4 (300 g).
The mixture was filtered through a celite pad (1 cm celite on a 2 L
sintered glass funnel) and the filter cake was rinsed with
dichloromethane (200 mL.times.2). The filtrate was concentrated to
.about.{fraction (1/10)} of its original volume, then methyl
tert-butyl ether (2 L) was introduced slowly with agitation to
induce crystallization. The mixture was gently stirred overnight at
room temperature. The precipitate was filtered, washed with methyl
tert-butyl ether (500 mL.times.2) and dried under high vacuum to
give the 2.degree.-amine HCl salt 7 as an almost white, low-density
powder, 306.45 g (83%, 98% LC). .sup.1H NMR (.delta., CDCl.sub.3):
9.77 (s, br, 2 H), 8.40 (d, J=4.0 Hz, 1 H), 7.50 (d, J=7.5 Hz, 1
H), 7.23 (dd, J.sub.1=7.6 Hz, J.sub.2=4.6 Hz, 1 H), 4.37 (dd,
J.sub.1=10.1 Hz, J.sub.2=5.4 Hz, 1 H), 3.60 (t, J=7.2 Hz, 2 H),
3.22-3.01 (m, 2 H), 3.00-2.76 (m, 2 H), 2.62-2.50 (m, 1 H),
2.42-2.16 (m, 2 H), 2.02-1.62 (m, 5 H), 1.50 (s, 18 H) ppm;
.sup.13C NMR (.delta., CDCl.sub.3): 152.5, 149.4, 146.9, 137.8,
133.2, 123.7, 82.3, 57.2, 45.0, 44.3, 27.9, 27.3, 25.8, 24.5, 23.5,
20.0 ppm; MS (M/z): 420, 320, 220.
[0125] Alkylation 19
[0126] The solid 2.degree.-amine HCl salt (Va') (301.77 g, 0.663
mol) was placed in a 2 L, 3-neck RBF fitted with a mechanical
stirrer, a temperature probe, and a nitrogen inlet. CH.sub.3CN (660
mL) was added, and the stirring was started. To this suspension was
added i-Pr.sub.2EtN (473 mL, 4 eq.), DMAP (0.02 eq.), and
N-Boc-chloromethylbenzimidazole (VI) (185.75 g, 1.05 eq.). The
mixture was stirred at 60.degree. C. under N.sub.2 until aliquot
NMR indicated completed reaction.
[0127] All volatiles were removed by rotary evaporation. The
residue was partitioned between water (3 L) and EtOAc (2 L). The pH
of the aqueous was adjusted to 2-3 with aqueous HCl (6 M). The
layers were separated and the aqueous was re-extracted with EtOAc
(2 L.times.2). The organic extracts were combined and concentrated
to dryness to give the product as a dark brown thick paste,
.about.420 g (some solvent remained). This material was used
directly in the subsequent reaction without further purifications.
.sup.1H NMR (.delta., CDCl.sub.3): 8.34 (d, br, J=4.1 Hz, 1 H),
7.80 (dd, J.sub.1=7.4 Hz, J.sub.2=4.1 Hz, 1 H), 7.68 (dd,
J.sub.1=5.8 Hz, J.sub.2=3.3 Hz, 1 H), 7.30-7.20 (over lapped with
CHCl.sub.3 signal, 3H), 6.94 (dd, J.sub.1=7.4 Hz, J.sub.2=4.6 Hz, 1
H), 4.62 (1/2 AB quartet, J=15.6 Hz, 1 H), 4.45 (1/2 AB quartet,
J=15.6 Hz, 1 H), 4.22 (dd, J.sub.1=9.6 Hz, J.sub.2=5.9 Hz, 1H),
3.40 (t, J=7.0, 2 H), 2.90-2.58 (m, 4 H), 2.20-2.04 (m, 1 H),
2.03-1.78 (m, 3 H), 1.68 (s, 9H), 1.75-1.60 (m, 2H, overlapping
with .delta.1.68 signal), 1.42 (s, 18 H), 1.54-1.24 (m, 2H,
overlapping with .delta.1.42 signal) ppm; MS (M/z): 550, 450,
350.
[0128] Deprotection 20
[0129] A solution of crude tri-Boc (VIIa') (320 g, .about.0.49 mol)
in THF (300 mL) was added to aqueous HCl (1 M, 4.4 L) with vigorous
stirring. The mixture was stirred at 20.degree. C. for 20 h. An
aliquot sample was obtained by partitioning between saturated
Na.sub.2CO.sub.3 and dichloromethane, extracting the organic layer,
and drying under high vacuum to obtain a residue. The residue was
taken up with CDCl.sub.3 and used for NMR to indicate complete
reaction.
[0130] The reaction mixture was cooled to 0.degree. C. and adjusted
to pH 6 with NaOH (10 M, total 520 mL added). The mixture was
extracted with DCM (1.5 L.times.3). Additional base was added as
needed to maintain pH 6. The aqueous was subjected to further
decolorization and extractions.
[0131] A 2 L portion (expect 77 g product) of the aqueous was
treated with charcoal (15.4 g, .about.20% w/w of expected product
amount) by stirring vigorously under N.sub.2 at room temperature
for 0.5 hour. The mixture was filtered through a celite pad (5 mm
celite on a 350 mL sintered glass funnel), and the filter cake was
washed with water (100 mL). The filtrate was adjusted to pH 9-10
with NaOH (4 M) and extracted with DCM (600 mL.times.2). Additional
base was added to maintain the pH during extractions. The combined
extract was washed once with NaOH (1 M, 100 mL) and stirred with
anhydrous Na.sub.2SO.sub.4 (140 g) for 1 hour under N.sub.2. The
mixture was filtered and the filter cake was washed once with DCM
(200 mL). The filtrate was concentrated by rotary evaporation (bath
45.degree. C.). A small amount of iso-propyl acetate (.about.50 mL)
was added and the mixture was re-evaporated until distillation
almost stopped. Pre-heated iso-propyl acetate (400 mL, 50.degree.
C.) was used to dissolve the residue. A small amount of seed
crystals were added and the mixture was allowed to cool to room
temperature overnight with vigorous stirring. The precipitate was
collected by filtration and was washed once with iso-propyl acetate
(50 mL). The filter cake was suction-dried under a stream of
N.sub.2 and further dried under high vacuum to give compound of
Formula I, freebase. Total 60.37 g (78%), white crystalline powders
(99.2% by LC-MS, 99.98% e.e.)
EXAMPLE 3
Large Scale Synthesis of
--(1H-benzimidazol-2-ylmethyl)-N'-5,6,7,8-tetrahy-
droquinolin-8-yl-1,4-butanediamine
Synthesis of N,N-di-tert-butoxycarbonyl-4-aminobytyraldehyde
(IIIa)
[0132] 21
[0133] Dimethyl-4-aminobtyraldehyde acetal (670 g, 5.0 mol, 1.0 wt.
eq.) was charged to a vessel. THF (1.68 L, 2.5 vol.) was added, and
the solution was cooled to 10-15.degree. C. Di-tert-butyl
dicarbonate (1.10 kg, 5.0 mol, 1.0 eq., 1.64 wt.) was dissolved in
THF (1.00 L, 1.5 wt.) at 0-20.degree. C., and the solution was then
added to the solution of the acetal, maintaining an internal
temperature of 10-15.degree. C. A line rinse of THF (335 mL, 0.5
vol.) was then done. The solution was then warmed to 15-25.degree.
C., and was maintained at this temperature for 30-60 minutes, until
the reaction was deemed to be complete by GC or .sup.1H NMR
(CDCl.sub.3). The reaction mixture was then concentrated under
vacuum at 15-25.degree. C. to 2 vol (1.35 L). THF (3.35 L, 5 vol.)
was then added, and the concentration was repeated. The THF
additions and distillations were repeated until the tBuOH level in
solution was determined to be <5.0 mol % relative to
product.
[0134] THF (670 mL, 1.0 vol) was then added, and the solution was
cooled to -10.degree. C. isopropylmagnesium chloride (2.0M in THF,
2.76 L, 5.5 mol, 1.1 eq., 4.13 vol) was added to the monoprotected
amine at -12.degree. C. to -8.degree. C. over 2-3 hours. A line
rinse of THF (330 mL) was then done, and the resulting solution was
stirred at -10.degree. C. for 30-40 minutes. A solution of
Di-tert-butyl dicarbonate (1.31 kg, 6.0 mol, 1.2 eq., 1.97 wt.) in
THF (1.00 L, 1.5 wt.) was then added, maintaining the temperature
below -8.degree. C. (over 2-3 hours). The reaction was then stirred
at -10.degree. C. until complete by .sup.1H NMR (<5 mol %
mono-protected amine). The reaction was then warmed to 0-20.degree.
C., and was quenched with a solution of potassium sodium tartrate
(40% w/w, 5.3 L, 8 vol). After stirring for 30-60 minutes, the
layers were separated, and the organic layer was washed with water
(2.0 L, 3.0 vol.) The organic layer was then concentrated to 4 vol.
(2.7 L) under vacuum at <25.degree. C.
[0135] Acetic acid (3.35 L, 5.0 vol) was then added to the
di-protected amine solution at 25-30.degree. C. Sodium chloride (67
g, 0.1 wt.) in water (1.68 L, 2.5 vol.) was then added, and the
reaction was stirred at 25-30.degree. C. until complete by .sup.1H
NMR (<8% acetal). A solution of 50% w/w aqueous sodium hydroxide
was then added to the solution at <30.degree. C. until the pH
was 8-9. Heptanes (2.0 L, 3.0 vol.) was then added, and the layers
were separated. As second heptane wash (2.0 L) was performed, and
the combined organic layers were dried over anhydrous sodium
sulfate, filtered, and concentrated to 3 vol. (2.0 L) at
<25.degree. C. The aldehyde solution was stored at 0-5.degree.
C. until required. Yield: 1.01 Kg by NMR assay (70% or a solution
78% pure by GC).
[0136] Reductive Amination 22
[0137] To a solution of the (S)-8-amino-5,6,7,8-tetrahydroquinoline
(2.5 mol, 1.0 eq.) in THF (7.5 L, 3 vol) was added sodium carbonate
(240 g, 2.5 mol, 1.0 eq.). The solution was cooled to 0-5.degree.
C., and the solution of aldehyde IIIa in heptanes (1.0 eq., ca. 3
vol.) was added. The reaction was then warmed to 20-25.degree. C.,
and was stirred for 1 h. Analysis by .sup.1H NMR was used to
determine stoichiometry, and the amount of aldehyde required to
achieve complete conversion. Extra aldehyde solution was added, as
necessary, until completion by .sup.1H NMR was achieved (<5% mol
aldehyde, >95% mol. imine). The mixture was then filtered,
rinsing the filter with THF (2.times.2.5 L). The imine Iva solution
was held at 0-5.degree. C. under nitrogen.
[0138] THF (13.75 L,5.5 vol) was added to a vessel, followed by the
portionwise addition of zinc chloride (510 g, 3.75 mol),
maintaining the temperature below 20.degree. C. The solution was
then stirred for 1-2 hours, and sodium borohydride (95 g, 2.5 mol)
was added to the solution. The mixture was then stirred for 2-3
hours, before being cooled to -20 to -30.degree. C. The imine
solution from above was then added, maintaining the temperature
below -20.degree. C. The reaction was then stirred for 1-2 hours at
-20 to -30.degree. C., before being checked by .sup.1H NMR (<5%
imine expected) on an hourly basis. Once the reaction is complete,
the solution is added to a 25% w/w aqueous ammonium chloride
solution (7.5 L). Dichloromethane (7.5 L) was added as a line
rinse. A 6M HCl solution was added until the pH was 4.5 to 5.5. The
aqueous and organic layers were then separated, and the organic
layer was washed with a mixture of 25% w/w aqueous NH.sub.4Cl (7.5
L) and concentrated aqueous ammonia (7.5 L). The layers were then
separated, and the wash of the organic layer was repeated, and the
layers were once again separated. Water (7.5 L) was then added to
the organic layer. 6N HCl was added slowly, with agitation, until
the pH of the aqueous layer was 2.0 to 2.5. The layers were then
separated, and the aqueous layer was washed with dichloromethane
(7.5 L). The organic layers were then combined, and dried with
anhydrous sodium sulfate (1.0 kg). The mixture was stirred for
approximately one hour, before being filtered. The filtrate was
concentrated under vacuum (at 30-35.degree. C.) to a volume of
approximately 2 L. TBME (7 L) was added at 30-35.degree. C. at a
constant rate over at least two hours to initiate precipitation of
the product Va. The slurry was then cooled to approximately
-10.degree. C. and was aged for 1-2 hours before being filtered.
The filter cake was then washed with TBME (2.times.1.5 L), and was
then dried under vacuum at <50.degree. C. until the residual
TBME was <0.1% w/w. The yield of Va was 957 g (2.09 mol, 83%
from II).
[0139] Alkylation and Deprotection 23
[0140] To a vessel was added Va (740 g, 1.63 mol) and
tetrabutylammonium iodide (TBAI, 118 g, 0.032 mol, 0.02 eq.),
followed by acetonitrile (740 mL). Diisopropylamine (1.15 L, 6.52
mol, 4.0 eq) was then added, and the mixture was heated to
60-65.degree. C. In a second vessel, VI (420 g, 1.60 mol, 0.98 eq.)
was dissolved in acetonitrile (800 mL). The solution of VI was then
added to the solution of Va, maintaining the temperature at
60-65.degree. C. The reaction was stirred for 1-2 hours, and then
the ratio of residual Va to VI was determined by .sup.1H NMR. If
necessary, extra VI is added to achieve equal stoichiometry between
the residual starting materials. The reaction was then stirred
until <0.35% mol residual VI is achieved by .sup.1H NMR.
[0141] The reaction was then cooled to 20-25.degree. C.
Concentrated commercial ammonium hydroxide (225 mL) was then added,
and the reaction was stirred at 20-25.degree. C. for 1 hour. Water
(750 mL) was then added to the reaction mixture, and the biphasic
mixture was then added to a separate vessel containing HCl (35%
w/w, 1.5 L). Acetonitrile (750 mL) was then used as a line rinse.
The reaction was then stirred at 35-40.degree. C. until complete by
.sup.1H NMR. Water (2.25 L) was then added, and the mixture was
distilled under reduced pressure at 30-40.degree. C. to
approximately 3 L. The level of acetonitrile was determined by NMR
(if>3% w/w, more water is added, and the distillation is
repeated).
[0142] The mixture was then cooled to 15-25.degree. C., and
dichloromethane (1.5 L) is added. The pH of the aqueous layer was
adjusted to >12.5 by the addition of 25% w/w aqueous sodium
hydroxide. The solution was then air sparged for 2-2.5 hours at
15-25.degree. C. The pH of the aqueous layer was adjusted to
5.0-5.5 with 6N HCl, and the layers were separated. The yield of
the reaction, as determined by .sup.1H NMR assay, was 82%. The
aqueous layer could then be treated with charcoal and carried
forward to the freebase crystallization as per Example 2.
[0143] It is understood that the examples and embodiments described
herein are for illustrative purposes only and that various
modifications or changes in light thereof will be suggested to
persons of skill in the art and are to be incorporated within the
spirit and purview of this application and the scope of the claims.
All publications, patents, and patent applications cited herein are
hereby incorporated by reference.
[0144] Citation of the above documents is not intended as an
admission that any of the foregoing is pertinent prior art, nor
does it constitute any admission as to the contents of date of
these documents.
* * * * *